That will help determine if Short term capital gain (ordinary income) or Longterm capital gains.  

There is likely a phone number and persons name that will come up, that you can reference, since he is having bills that arrive to the mailbox and packages to the door with his name on them.You could make it a pre-condition to the seller that he allow a background check on the tenant before closing and your offer is contingent on your approval.Neighbors typically know what's going on in the neighborhood and will know who the guy is and if he is a trouble maker.He probably has a car and a private detective can run the plates.And so on.The information is readily available is the knowledge is worth knowing.

I've heard that the down payment percentages for investment properties can be higher compared to primary residences.Specifically, I'm looking for insights on:The typical down payment percentages required by conventional lenders for investment properties.Any differences in requirements for single-family homes versus multi-unit properties.Experiences with different lenders and any recommendations for those offering favorable terms for investment properties.Any tips for negotiating better terms or finding lenders with more flexible down payment options.For context, this will be my second property, and I have a good credit score and a stable income.

Which one (usually, and I understand it's not simple) has a better resale and long-term potential?

Fannie/Freddie have more restrictions in terms of experience and net worth to qualify.

It will also depend on your goals short and long term and why you're investing. 

Short-term goals might include acquiring your first property, learning the basics of property management, or networking with other investors.

Try a long term lease option. 

I am looking for refinance short term rental.

For example, if the tenant breaks a window and you spend $250 repairing it (materials & labor), you bill that back to them to be paid with the next rent payment.